SU1443103A1 - D.c. to quasi-sine a.c. converter - Google Patents

Abstract

The invention relates to the field of electrical engineering and m. used in power supply and electric drive systems. The goal is to increase the quality of the output voltage by decreasing its harmonic ratio. In this device, in addition to the two main voltages of the carrier frequencies f and fj, additional voltages that are similar in shape and are shifted in phase by an angle of 2n / t. The additional voltages of the carrier frequencies with the same phase shift as well as the main voltages of the same frequencies are summed in pairs in pairs. Total voltages subject to amplitude-pulse; 2nd kind of modulation of the corresponding phase of the control voltage frequency f3. The obtained modulated voltages are summed up among themselves. 2 hp f-ly, 6 ill. (L with

Description

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The invention relates to electrical engineering and can be used in power supply and electric drive systems for converting a constant voltage to an alternating voltage.

The purpose of the invention is to increase the quality of the output voltage by reducing its harmonic coefficient.

FIG. I presents a converter block diagram; in fig. 2 is a control block diagram; in fig. 3-6 are diagrams explaining the process of forming the output voltage, respectively, for cases when the voltage of the carrier frequencies is rectangular and sinusoidal.

Constant voltage to alternating voltage quasi-in-voltage converter (Fig. 1) for case m 3 contains three-phase inverter units 1 and 2, made in the form of three single-phase inverter cells with outputs, matching transformers, demodulators 3-5, made for example, according to the single-phase bridge inverter scheme on fully controlled switches with double-sided conductivity, summation block 6, frequency sensors f 7–7 f, and carrier frequencies f and e (FIG. 2), implemented, for example, on a scaling ring circuit, dividers 10-12 frequencies and s giving the generator 13.

The summation unit can be executed in the inside of a three-rod filter. Transformer 14 (Fig. 16)

The Converter operates as follows.

At the outputs of each of the three-phase (t 3) frequency adjusters 8, 9, 7 (Fig. 5a), two-way high-polarity high-frequency pulses, respectively, f, fj, fj, having a mutual phase shift 2 UZ. The working time to the dials receives from the master oscillator 13 through the dividers 10-12 frequencies. If the frequency adjusters are made according to the recalculated ring scheme, then the values of the sharing factors are reduced by 3 times (in general, by m times). The signals from the outputs of the setting units 8 and 9 are fed to the control inputs of the inverter cells 1 and 2 through phase-shifting devices that implement the phase shift at adjustable angles rf ,, -d, respectively

"one,

- 0 ,. as a result of the outputs

cells 1 and 2 are rectangular

032

voltage pulses of equal amplitude with a pause of adjustable duration 2o (, and 2 cVj, respectively, fit and 2 frequencies with mutual phase retraction 2ТГ / 3 (fig.Za-e). The same outputs of the inverter cells are connected in series. The output voltages of the cells are added together, and in such a manner, modulated voltages (Fig. 3, 3, 3) are fed to the power inputs of the demodulators 3-5, respectively. Signals from the same outputs of the setpoint 7 frequency f are sent to the control inputs of the demodulators (Fig. 3c, l, m) At the output of demodulators, 3-5 are received for the same and (fig. Yes, b, c) with amplitude-pulse-width modulation and frequency of the first harmonic f, and in phase with the first harmonic. The output voltages of the demodulators are actually the result of multiplying the signals fed to the power and control The inputs of the demodulators are connected in series, their output voltages are summed up (summation in a common circuit) and, thus, the output voltage of the converter is obtained (Fig. 4g) frequencies f with a reduced harmonic coefficient due to the fact that high frequency harmonics that form three-phase systems (in general (ha-phase) systems do not fall on the converter output. The broken line (Fig. 4g) is formed by low-frequency harmonics that are multiples of f and represents is the output voltage of the converter without subharmonic components, which are easily eliminated by a small filter.

Converter with filter transformer works as follows.

The output voltages of demodulators 3-5 (Fig. 4a, b, c) are fed to the windings of a three-rod filter transformer 14 (Fig. I) through the load of the converter. The first harmonic voltage f (FIG. 4a, b, c) is phase-locked, and the filter transformer operates in the short circuit mode (its windings are actually connected in parallel, which is equivalent to the short circuit of a three-phase transformer), and harmonic without distortion enters

31

converter output Flo with respect to the high-voltage harmonics forming the three-phase systems, the windings of the filter-transformer are connected in the usual way a star and, delaying these harmonics, does not pass them to the output of the converter. At the output of the converter, a voltage is formed that is identical in form to the total output voltage of the demodulators 3-5 (Fig. 4g) and differs from the latter only by a factor of 3 reduced (in general, m times) amplitude the harmonics have three times the amplitude, and the harmonics forming the three-phase systems are zero) The voltages of the filter transformer of the filter transformer are applied (Fig. 4d, e, f), the voltage is high frequency, so the mass and dimensions of the filter transformer are small.

An example of the phase voltages of a sinusoidal carrier frequency, f, and f is shown in FIG. 5 ae, in fig. 5g, g, and are the results of the summation of the voltages of the phases, respectively (Fig. 5a, d), c (Fig. 56, e) and C (Fig. 5c, e). By multiplying the signals, respectively (Figs. 5g, 3, and 5k, l, m), modulated voltages are obtained (Fig. 6a, b, c). As a result of their summation, the output voltage is obtained (Fig. 6g);

The use of the proposed converter provides a significant improvement in the quality of the output voltage by reducing its harmonic coefficient, namely due to the fact that the output voltage does not have a number of harmonics forming t-phase systems during its formation, and, in addition, the presence of pauses duration 2 "/, 2d, 2 at phase voltages f, f, 3 allows adjustment within wide limits or stabilization of the amplitude of the first harmonic of the output voltage while maintaining the harmonic Onik at a minimum.

Claims (3)

1. Constant-to-voltage converter into alternating quasi-sinusoidal voltage, containing two inverter cells, controlling 034 the inputs of each of which are connected to one of the setting units of the carrier frequencies f, and f .; , the outputs of these cells are connected in series and through a demodulator made on the AC switches connected to the output outputs of the device, and the control inputs of the demodulator are connected to the output of the frequency setting unit f3 (f, fj) and the unit Controls with a master frequency generator, which is designed to improve the quality of the output voltage while expanding the range of possible use over the power range, 2 (t -1) inverters are entered into it cells and (t-1) demodulators, and frequency adjusters, fj, fj are made m-phase, each of which is connected through one of the three frequency dividers entered into the control unit, respectively, with coefficients of 75f K, K, K, - and K, where 1 I I 7 K, is an integer with the output of the master Frequency generator F tK i f,, outputs of m-phase frequency adjusters f, f. f are connected respectively to the control inputs 2ga of inverter cells and mn demodulators, the power inputs of the latter are connected to pair-series-connected outputs of the inverter cells controlled from frequency adjusters f, and f2 having the same phase shift on the control input, and their outputs connected via a summation unit to the output outputs of the converter. 2. A converter according to claim 1, characterized in that in the summation unit the outputs of hectares of demodulators are connected in series. 3. The transducer according to claim 1, T is characterized by the fact that the summation unit is made in the form of a t-phase filter transformer with windings located on m rods x m, and one of the same polarity output terminals of the demodulators are combined, form one output view of the converter, and the others are interconnected through the indicated windings of the filter transformer, forming the second output terminal of the converter. 0- 0- 0- 0- Bb / k Phases. i - / 7 Phie. 2  Lj lj m n Ryo n n n LJ LJ LJ L: n n n n J LJ LJ LJ LJ 1 n n n П П Lj lj lj lj lj l rS r nn 1 1., nn r, V v v r b pi (in r g . f VVu VVVSnnAL  yu uul-pr jl .GU Lupp .yAj u unuJXr r iV ljyi " fat. n GP n n  LJ LJ LT n n n n r Well DO UU SrVi  XX / X / N WVVx . A / VV Yw / Vwv Well L / g. ff